An Ultrasensitive Explosives Detector

An Ultrasensitive Explosives Detector

Bomb detector: Chemically treated silicon nanowires at the center of this glass chip change conductance when exposed to minute traces of explosives in air or liquids.

A nanowire sensor made by researchers at Tel Aviv University can detect extremely small traces of commonly used explosives in liquid or air in a few seconds. The device is a thousand times more sensitive than the current gold standard in explosives detection: the sniffer dog.

The sensor could be cheaply produced and incorporated into a handheld instrument for detecting buried landmines or concealed explosives at security checkpoints, according to Fernando Patolsky, a chemistry professor who led the work, which was published in the journal Angewandte Chemielast week. The researchers are developing a portable instrument based on the technology. Their first prototype is about the size of a brick. “We could put the sensors everywhere in an airport, in every corner of a shopping mall,” Patolsky says.

Trained dogs have historically been used to sniff out bombs and landmines because they can smell explosives at concentrations of just a few parts per billion. But it takes tens of thousands of dollars to train and maintain a sniffer dog, so handheld detectors promise a cheaper and more portable solution.

The nanowire array isn’t the first device to achieve canine levels of explosive-sniffing sensitivity. A system developed by ICx Technologies, based in Arlington, Virginia, can detect vapors given off by explosives with a sensitivity matching that of a canine nose. Instead of nanowires, the ICx system uses polymers that glow or stop glowing in response to traces of explosive in a vapor in a few seconds. This device is being used in battlefields in Iraq and Afghanistan, and the U.S. Transportation Security Administration recently started using it at airports, but most airports still rely on microwave oven-sized instruments that take minutes, rather than seconds, to detect explosives in swabs taken from luggage or passengers’ skin.

The new Tel Aviv University device is a thousand times more sensitive than any existing detector, including the ICx device. The researchers have used it to detect TNT and the plastic explosives RDX and PETN at concentrations lower than one part per trillion in a few seconds.